Recently, accurate control of an internal combustion engine conforming to the surrounding environment such as temperatures is sought to enhance fuel economy, reduce emissions, and the like. For example, under high humidity environment, an air-fuel mixture is unlikely to be ignited owing to an increase in the heat capacity of the air-fuel mixture, and, even when the air-fuel mixture fires, the flame is unlikely to spread.
Consequently, the combustion characteristics of the air-fuel mixture may become deteriorated. It is therefore desired to provide a countermeasure thereto.
Patent Literature 1 describes an ignition device that increases the air-fuel ratio to thereby decrease NOx under a high humidity environment. However, this ignition device increases the air-fuel ratio in a state in which the air-fuel mixture is difficult to fire due to the high humidity environment and the flame is unlikely to spread. This may result in blow-off of the flame.